To create your own figure for Poser or daz Studio (instead of a character based on base figure) you will need a 3d modelling program that can export to .obj format. Poser and DS are for posing, rendering and animating. They have tools for creating characters based on prebuilt figures but not the tools to build a 3d model from scratch.
To build from scratch you need lightwave, max or their commerical competitors or to use open source modellers like blender or wings3d (which are free).